Hey Guys,

 

Been having this issue intermittently ever since i got the car. Its very strange as the missfire is always on the last right cylinder next to the firewall. Its completely random, most days its fine but every other week it comes back and then i get rough idle and popping sound from the exhaust.

 

I am really stumped as to what this might be. Just had a service done so new spark plugs and oil change etc. I changed the coil packs over and its still the same so not that either.

 

I hardly know much but from all the reading and advice from people, its coming back as either the fuel injectors or the PTU? Any help would be great as I am a complete newbie.

Im getting the same on the black one, but its a loom issue always drops cylinder 4 at the moment, very random when it does it, but i know exactly what the cause is, as the engine loom is so old, there is a break in the cable somewhere, ive already changed the plug, but its further along than where i thought it was, it comes back once the wire is wiggled. yours could be the same issue could be the loom, take the connector off the injector and give the pins a bloody good clean, might be bunged up with 20 years of crap, the intermittent would point to either a connection issue or cable issue.

 

I had the same issue with the car, but thought id sorted that out :(

Im getting the same on the black one, but its a loom issue always drops cylinder 4 at the moment, very random when it does it, but i know exactly what the cause is, as the engine loom is so old, there is a break in the cable somewhere, ive already changed the plug, but its further along than where i thought it was, it comes back once the wire is wiggled. yours could be the same issue could be the loom, take the connector off the injector and give the pins a bloody good clean, might be bunged up with 20 years of crap, the intermittent would point to either a connection issue or cable issue.

 

I had the same issue with the car, but thought id sorted that out :(

 

By connectors of the injectors you mean the fuel injectors? or the one at the top of the coilpacks.

 

Also i tried wiggling the cable on top of that cylinders coil pack and still didnt make a difference!!

Hi,

 

the injectors sit down under the plenum, if you look down behind the coil packs you can see the connectors.

 

they are hard to get to and there is (like on all other connectors) a metal clip.. you need a bit of patience (remove the plastic cover first)

 

there is also a connector to the fuel rail temp sender unit (passengers side) .. :)

Hi,

 

the injectors sit down under the plenum, if you look down behind the coil packs you can see the connectors.

 

they are hard to get to and there is (like on all other connectors) a metal clip.. you need a bit of patience (remove the plastic cover first)

 

there is also a connector to the fuel rail temp sender unit (passengers side) .. :)

 

So would i need to take the coilpacks out? or the plenum cover? srry but never done it before :P

Edited October 8, 201213 yr by Javelin

no... I should have been more explicit....

 

if you look down behind the coil packs (towards the middle of the engine) you will see the connectors the leads run parallel with the coil packs leads.

 

just remove the plastic cover on the top of the engine.

 

you will need a couple of very thin flat long screwdrivers to undo the metal clips.

 

this will help

 

http://www.twinturbo.net/nissan/300zx/tech/plenum/plenum.aspx

Edited October 8, 201213 yr by Medallion Man

no... I should have been more explicit....

 

if you look down behind the coil packs (towards the middle of the engine) you will see the connectors the leads run parallel with the coil packs leads.

 

just remove the plastic cover on the top of the engine.

 

you will need a couple of very thin flat long screwdrivers to undo the metal clips.

 

this will help

 

http://www.twinturbo.net/nissan/300zx/tech/plenum/plenum.aspx

 

Thanks, well while i was taking my plenum cover off, i noticed a fuel leak near that cylinder. I was wondering if this had anything to do with it?? every second there was a drop of petrol dripping out.!!

 

 

 

Not sure if you can see but this is the valve that is leaking petrol, would this by any chance causing it??

Edited October 8, 201213 yr by Javelin

fuel pressure regulator, return feed to the tank...

 

most definitely get that sorted...

as far as making it run rough, I'm not sure, if the leaks is after the regulator and there is nothing wrong with it (as fas as keeping the pressure in he fuel line) then I can't see it causing an issue (other than a fire risk!!!).

However is the leak is pre the regulator then a lower fuel pressure may cause some problems.

fuel pressure regulator, return feed to the tank...

 

most definitely get that sorted...

as far as making it run rough, I'm not sure, if the leaks is after the regulator and there is nothing wrong with it (as fas as keeping the pressure in he fuel line) then I can't see it causing an issue (other than a fire risk!!!).

However is the leak is pre the regulator then a lower fuel pressure may cause some problems.

 

Well would it cause the misfire? or would that still be the fuel injector connectors

lack of fuel pressure would give you miss fire symptoms .. as it needs a certain amount of pressure .. for the injectors to work correctly

Backfiring generally means unburnt fuel in the exhaust which means ignition not fuel delivery problem. So concentrate on coil pack connections. If it only happens when warm consider failing coil pack too.

It happens randomly and I have swapped the coils packs over from working cylinder and it's the same cylinder!! Also just had new sparks plugs put in. So must be fuel injector connectors or the leak!

 

Would ignition coil cause this issue?

Edited October 9, 201213 yr by Javelin

Yeah, so just to confirm you have cleaned all connectors on the PTU, CAS & MAF.. etc.

 

you can test the resistance on the injectors and you can also check that they are firing but since its intermittent it "may be" more likely to be an electrical problem.

 

did you clean the injector connector?

OK, so it could be the PTU breaking down, do you have a series I or II PTU ? If you have a I, borrow a working one to test. If you have a II, it's almost certainly something else !

Yeah, so just to confirm you have cleaned all connectors on the PTU, CAS & MAF.. etc.

 

you can test the resistance on the injectors and you can also check that they are firing but since its intermittent it "may be" more likely to be an electrical problem.

 

did you clean the injector connector?

 

The fuel injector connectors? not yet need to get to it, been raining so far, not had a chacne to do anything

OK, so it could be the PTU breaking down, do you have a series I or II PTU ? If you have a I, borrow a working one to test. If you have a II, it's almost certainly something else !

 

series 1 i think

Ok Right just had a look, warning some newbie question but here it goes

 

I think this is the ptu, was wondering if it was series 1 or 2

 

 

Also when referring to fuel injector connectors are you referring to these?

 

Ok Right just had a look, warning some newbie question but here it goes

 

I think this is the ptu, was wondering if it was series 1 or 2

 

[ATTACH=CONFIG]66752[/ATTACH]

 

Also when referring to fuel injector connectors are you referring to these?

 

[ATTACH=CONFIG]66753[/ATTACH]

 

yes thats a S1, i tried changing it for a know working one, but it refused to start then, your best option would be going for a S2 ptu, and yes to the second picture thats a fuel injector, make sure you have a magnetic long flat head to get the little securing pin off as 9 out of 10 times it will fall on the engine in a location that is not accessible unless the plenum is removed.

Hey voda how do i take that connectors off? Do i need to take the screws at the bottom off? cause that would be bit hard without taking the plenum off, and which pin are you referring too?

 

Also with the s2 ptu would it be plug and play or does it need wiring in?

Hey voda how do i take that connectors off? Do i need to take the screws at the bottom off? cause that would be bit hard without taking the plenum off, and which pin are you referring too?

 

Also with the s2 ptu would it be plug and play or does it need wiring in?

 

Leave the screws, they are the end caps for the injectors, on the plastic connector that connects to the injector, there is a U shaped metal clip (pin) you need a precision flat head screw driver to push the ends down, this is usually where the connector tends to snap and break if its too old, once you have pushed both sides, you should see the end of the clip facing towards the middle of the engine, its at this point you take a magnatised flat head and remove the rest of the clip, put it some where safe and then carry on with the rest, have some stickers handy to label the injectors 1 to 6 so you know what one goes on where.

 

Give the male pins on the injector side a good clean with either a bit of sand paper, or a woman's nail file, or something else rough that can get in there, no doubt you will find loads of oxidiastion when doing (normal for a 20 year old engine) cant remember if ive already done that on that car, having 3 zeds gets a bit confusing as to whats been done on what one.

 

Anyway, get some connector grease in there as well once cleaned up to help prevent it doing it again, before putting the connector back onto the injector, refit the securing clip (little metal U shaped bit) then reconnect to the injector.

 

As for the S2 ptu, would depend if someone sells one with a fitting harness, or they just supply it with the connectors with wires coming out the end that you then have to solder into the exsisting loom.

Leave the screws, they are the end caps for the injectors, on the plastic connector that connects to the injector, there is a U shaped metal clip (pin) you need a precision flat head screw driver to push the ends down, this is usually where the connector tends to snap and break if its too old, once you have pushed both sides, you should see the end of the clip facing towards the middle of the engine, its at this point you take a magnatised flat head and remove the rest of the clip, put it some where safe and then carry on with the rest, have some stickers handy to label the injectors 1 to 6 so you know what one goes on where.

 

Give the male pins on the injector side a good clean with either a bit of sand paper, or a woman's nail file, or something else rough that can get in there, no doubt you will find loads of oxidiastion when doing (normal for a 20 year old engine) cant remember if ive already done that on that car, having 3 zeds gets a bit confusing as to whats been done on what one.

 

Anyway, get some connector grease in there as well once cleaned up to help prevent it doing it again, before putting the connector back onto the injector, refit the securing clip (little metal U shaped bit) then reconnect to the injector.

 

As for the S2 ptu, would depend if someone sells one with a fitting harness, or they just supply it with the connectors with wires coming out the end that you then have to solder into the exsisting loom.

 

managed to get hold of a ptu with the harness should arrive soon, and thanks a lot for the descriptive information, it is very useful for me. Gonna have some free time on friday and will give it all a try :)

 

But if i remember right you did say you gave the connectors a good scrub and they stoped the rough idle etc, in one of your posts!! o.O

Edited October 10, 201213 yr by Javelin